1. Field of the Invention
The present invention relates to a system for measuring characteristics of an FET (field effect transistor) in which a gate voltage in the form of a pulse having a set output voltage from a pulse generator is applied to the gate of an FET in order to measure drain current flowing through the FET. More specifically, the present invention relates to adjustment of the set voltage of the pulse generator so that a desired voltage is accurately applied to the gate of the FET.
2. Description of the Related Art
The IV (current-voltage) characteristics of an FET are determined by applying a predetermined DC (direct current) voltage to the gate of the FET while a predetermined bias voltage is applied to the drain.
However, for measuring the IV characteristic of an advanced MOSFET, such as a SOI (silicon on insulator) MOSFET, a strained-silicon MOSFET, or a MOSFET using a high-k (high dielectric constant) gate insulator, the known measuring method in which a DC voltage is applied to the gate of the FET cannot provide a reliable measurement result of the IV characteristic because of a self-heating phenomenon exhibited by the FET.
Accordingly, it has been proposed to apply a short-duration pulse to the gate of the FET (e.g., refer to K. A. Jenkins and J. Y-C. Sun, IEEE Electron Device Letters, Vol. 16, No. 4, April 1995, p 145 to 147). This allows the semiconductor device to operate without producing heat, thus making it possible to provide a measurement result that is not affected by heat production.
An output pulse from a pulse generator is input to the gate of an FET. However, since the value of a voltage output from the pulse generator is generally guaranteed only for a sufficiently long pulse width, the output voltage is in many cases not sufficiently stable for a pulse width of 100 ns or less. Thus, with a pulse having a pulse width of 100 ns or less, it is not desirable to directly use the output of the pulse generator from the viewpoint of providing high measurement accuracy.